Method and apparatus for stacking sheet materials

ABSTRACT

A sheet stacking and pallet loading system configured to stack sheets of material on a first pallet while holding a second pallet in a staging position above the first pallet. The system can include an elevator for supporting the first pallet in a loading position while the sheets are stacked on the first pallet. After a sufficient quantity of sheets has been stacked thereon, the elevator can lower the first pallet from its loading position. The second pallet can then be lowered from its staging position such that the sheets can be stacked thereon. The system can further include extendable pallet supports which can be extended to support the second pallet while the first pallet is being lowered by the elevator. The pallet loading system can further include a pallet-grasping assembly having, first, a frame movable along a track and, second, one or more end-effectors movable relative to the frame for engaging a pallet.

BACKGROUND

1. Field of the Invention

The present invention generally relates to stacking sheets of materialon a pallet, for example, and, in addition, to exchanging pallets once asufficient, or predetermined, quantity of sheets has been stacked on thepallet.

2. Description of the Relevant Art

Many materials produced by strip mills, including sheet metal, forexample, are typically sold in large, coiled rolls. Those purchasingthese large, coiled rolls and desiring to manufacture various productsfrom the sheet metal, for example, often find it necessary to have thesheet metal slit into narrow strips on a slitting line and/or otherwisecut to width. In various circumstances, as a result, the sheet metal isslit longitudinally along the length thereof to sizes suitable forparticular products and/or stamping processes, for example. Variousexemplary devices and methods for slitting material and/or cuttingmaterials to width are disclosed in U.S. Pat. No. 4,298,633, entitled“METHOD AND APPARATUS FOR TENSIONING METALLIC STRIPS ON A SLITTINGLINE”, which issued on Nov. 3, 1981; U.S. Pat. No. 4,614,101, entitled“METHOD OF REWINDING SLIT METAL STRANDS”, which issued on Sep. 30, 1986;U.S. Pat. No. 5,373,766, entitled “SLITTER KNIFE HOLDER”, which issuedon Dec. 20, 1994; U.S. Pat. No. 5,421,535, entitled “METHOD ANDAPPARATUS FOR AUTOMATICALLY WINDING SCRAP METALLIC STRIP METAL”, whichissued on Jun. 6, 1995; U.S. Pat. No. 7,134,372, entitled “CNC SLITTERMACHINE”, which issued on Nov. 14, 2006, and U.S. patent applicationSer. No. 11/268,004, entitled “COMPENSATING STRIPPER RINGS FOR MATERIALSLITTING MACHINES”, which was filed on Nov. 7, 2005, the entiredisclosures of which are incorporated by reference herein. Otherexemplary slitters include HERR-VOSS® STAMCO® STRAND EXTENSIONER® and“Compu-Cut”™ machines available from the Herr-Voss Stamco Company inCallery, Pa.

Further to the above, there are a variety of shape defects that mayarise in flat rolled materials, especially in metal materials, forexample. Mill induced defects in metal materials can include, forexample, wavy edges, center buckles, quarter buckles, crossbow, and coilset. Such shape defects may be caused by misaligned rolls or othersubstandard equipment or manufacturing processes that can be found in anarray of processing lines. Regrettably, material related shape problemsresult in inefficient operations at downstream processing plants, andmaterial variability or inconsistency can cause production delays,customer dissatisfaction, and many other problems and potential costs.In view of the above, levelers have been developed to reduce suchdefects and problems and can be employed before the material has beenwound into a coiled roll and/or after the material has been unwound fromthe roll. Various exemplary devices and methods of leveling material aredisclosed in U.S. Pat. No. 4,635,458, entitled “LEVELING APPARATUS”,which issued on Jan. 13, 1987; U.S. Pat. No. 4,587,822, entitled“TENSION LEVELING APPARATUS”, which issued on May 13, 1986; U.S. Pat.No. 4,765,169, entitled “METHOD OF TENSION LEVELING NONHOMOGENEOUS METALSHEET”, which issued on Aug. 23, 1988; U.S. Pat. No. 5,255,549, entitled“TENSION LEVELER ROLL CLEANING SYSTEM AND METHOD”, which issued on Oct.26, 1993; and U.S. patent application Ser. No. 11/149,898, entitled “CNCLEVELER”, which was filed on Jun. 10, 2005, the entire disclosures ofwhich are incorporated by reference herein. Other exemplary levelersinclude HERR-VOSS® STAMCO® PRECISION LEVELER® machines available fromthe Herr-Voss Stamco Company in Callery, Pa.

Once the material has been unwound from their large, coiled rolls andsufficiently leveled and cut to width, if necessary, the material can becut into sheets. In various circumstances, sheet metal, for example, canbe fed into a shear, or cut-to-length line, and cut lattitudinally inorder to cut the sheet metal to length. Depending on various parameterssuch as the speed of the line, the length of the sheets, and thethickness of the material, for example, a shear may often comprise adown cut shear, a rotary shear, and/or a hydraulic shear. Exemplarycut-to-length processing lines are available from the Herr-Voss StamcoCompany in Callery, Pa. Once cut to length, the sheets can be stackedonto a pallet and, after a sufficient, or predetermined, quantity ofsheets has been stacked on the pallet, the finished pallet can beremoved from the processing line. In many circumstances, though, it isthe removal of the finished, stacked pallet and the placement of anempty pallet that causes interruptions in the processing of thematerial. What is needed is a sheet stacking device which can decreaseand/or eliminate such interruptions.

SUMMARY

In at least one form, a sheet stacking and pallet loading system can beconfigured to stack sheets of a material on a first pallet, for example,while holding a second pallet, for example, in a staging position abovethe first pallet. In various embodiments, the system can include anelevator for supporting the first pallet in a loading position whilesheets of material are stacked on the first pallet and, after asufficient, or predetermined, quantity of sheets have been stackedthereon, the elevator can lower the first pallet from its loadingposition.

In various embodiments, the second pallet can be lowered from itsstaging position into a loading position such that sheets of materialcan be stacked on the second pallet. In at least one embodiment, thesystem can further include extendable pallet supports which can beextended to support the second pallet in the loading position. Incertain circumstances, the second pallet support can be lowered onto theextendable pallet supports while the first pallet is being lowered byand/or removed from the elevator. The elevator can then be repositionedunderneath the second pallet and the extendable pallet supports can beretracted such that the second pallet can be supported by the elevator.Similar to the above, a third pallet, for example, can be held above thesecond pallet while sheets of material are stacked on the second palletsuch that the pallet exchange process can be repeated once again.

In various embodiments, the pallet loading system can be configured tograb, or grasp, a pallet and move it into a staging position. In atleast one embodiment, the pallet loading system can include a trackdefining a path and a frame movable along the path. In at least one suchembodiment, the pallet loading system can further comprise at least onepallet-engaging assembly movably mounted to the frame which can beconfigured to engage the pallet. In certain embodiments, a first palletengaging assembly can be moved relative to the frame to engage a palletin a first direction, a second pallet-engaging assembly can be movedrelative to the frame to engage the pallet in a second direction, and athird pallet-engaging assembly can be moved relative to the frame toengage the pallet in a third direction, wherein the first, second, andthird directions can be different. In at least one such embodiment, thefirst, second, and third directions can define a plane for holding thepallet.

This Summary is intended to briefly outline certain embodiments of thesubject application. It should be understood that the subjectapplication is not limited to the embodiments disclosed in this Summary,and is intended to cover modifications that are within its spirit andscope, as defined by the claims. It should be further understood thatthis Summary should not be read or construed in a manner that will actto narrow the scope of the claims.

BRIEF DESCRIPTION OF THE FIGURES

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is an elevational view of a sheet stacking and pallet loadingsystem in accordance with at least one embodiment of the presentinvention illustrating a pallet car positioned underneath a stack ofpallets which are supported by pallet support members;

FIG. 2 is a perspective view of the pallet car and the pallet supportmembers of the system of FIG. 1;

FIG. 3 is an elevational view of the system of FIG. 1 illustrating thestack of pallets being moved by the pallet car;

FIG. 4 is an elevational view of the system of FIG. 1 illustrating apallet grasping assembly engaged with a first pallet on the pallet car;

FIG. 5 is an elevational view of the system of FIG. 1 illustrating thepallet grasping assembly of FIG. 4 lifting the first pallet off of thepallet car;

FIG. 6 is a perspective view of the pallet grasping assembly of FIG. 4including three actuator assemblies configured for engaging a pallet;

FIG. 7 is another perspective view of the pallet grasping assembly ofFIG. 4 illustrating one of the actuator assemblies having anend-effector in an extended position and two of the actuator assembliesin retracted positions;

FIG. 8 is another perspective view of the pallet grasping assembly ofFIG. 4;

FIG. 9 is yet another perspective view of the pallet grasping assemblyof FIG. 4;

FIG. 10 is a top view of the pallet grasping assembly of FIG. 4;

FIG. 11 is an elevational view of the pallet grasping assembly of FIG.4;

FIG. 12 is a perspective view of one of the actuator assemblies of FIG.6 illustrated in an extended configuration;

FIG. 13 is another perspective view of the actuator assembly of FIG. 12illustrated in a retracted configuration;

FIG. 14 is another perspective view of the actuator assembly of FIG. 12illustrated in an extended configuration;

FIG. 15 is another perspective view of the actuator assembly of FIG. 12illustrated in a retracted configuration;

FIG. 16 is a detail view of a distal portion of the end-effector of theactuator assembly of FIG. 12;

FIG. 17 is an elevational view of the system of FIG. 1 illustrating thefirst pallet of FIG. 4 being held in a staging position by the palletgrasping assembly;

FIG. 18 is an elevational view of the system of FIG. 1 illustrating thefirst pallet of FIG. 4 being supported in a loading position byextendable pallet supports and illustrating first and second sheetsupports which have been pivoted downwardly to permit the first palletto pass thereby;

FIG. 19 is a diagram illustrating an actuator assembly configured tomove one of the sheet supports of FIG. 18 outwardly to allow the firstpallet to pass by the sheet supports and, in addition, move the sheetsupport inwardly once the first pallet has passed thereby in accordancewith at least one embodiment of the present invention;

FIG. 20 is an elevational view of the system of FIG. 1 illustrating asheet of material supported by the first and second sheet supports;

FIG. 21 is a perspective view of one of the sheet supports of FIG. 18 ina sheet-supporting configuration;

FIG. 22 is a perspective view of a sheet of material supported by thefirst and second sheet supports and, in addition, a pallet supported bythe extendable pallet supports of FIG. 18;

FIG. 23 is an elevational view of the system of FIG. 1 illustrating asheet of material being dropped onto the first pallet of FIG. 4 andillustrating the pallet grasping assembly en route to obtain a secondpallet;

FIG. 24 is a perspective view of the sheet support of FIG. 21 pivoteddownwardly into a sheet-dropping configuration;

FIG. 25 is an elevational view of the system of FIG. 1 illustrating anelevator being raised to support the first pallet and illustrating thepallet grasping assembly engaged with the second pallet;

FIG. 26 is an elevational view of the system of FIG. 1 illustrating theextendable pallet supports in a retracted position and illustrating thesecond pallet lifted off of the pallet car by the pallet graspingassembly;

FIG. 27 is an elevational view of the system of FIG. 1 illustrating theelevator of FIG. 25 being indexed downwardly as sheets of material arebeing stacked on the first pallet and illustrating the second pallet ina staging position positioned above the first pallet;

FIG. 28 is a partial cross-sectional view of an actuator for pivoting asheet support and an actuator for extending and retracting a palletsupport in accordance with at least one embodiment of the presentinvention wherein the sheet support is illustrated in adownwardly-pivoted, or sheet-dropping, position to allow a pallet to beplaced on the extended pallet support;

FIG. 29 is a partial cross-sectional view illustrating the sheet supportof FIG. 28 in a sheet-supporting position, a sheet of material supportedby the sheet support, and the pallet support of FIG. 28 in an extendedposition;

FIG. 30 is a partial cross-sectional view illustrating the sheet supportof FIG. 28 in a sheet-dropping position and the sheet of materialpositioned on the pallet of FIG. 28;

FIG. 31 is a partial cross-sectional view illustrating the elevator ofFIG. 25 supporting the pallet of FIG. 28 and illustrating the palletsupport of FIG. 28 in an extended position;

FIG. 32 is a partial cross-sectional view illustrating the elevator ofFIG. 25 supporting the pallet of FIG. 28 and illustrating the palletsupport of FIG. 28 in a retracted position;

FIG. 33 is a perspective view of the pallet support of FIG. 28;

FIG. 34 is an elevational view of the system of FIG. 1 illustrating thefirst pallet being lowered by the elevator of FIG. 25 and illustratingthe second pallet being placed on the extendable pallet supports of FIG.18 by the pallet grasping assembly;

FIG. 35 is an elevational view of the system of FIG. 1 illustrating thefirst pallet positioned on a discharge conveyor and illustrating a sheetof material supported by the sheet supports of FIG. 18;

FIG. 36 is an elevational view of the system of FIG. 1 illustrating thefirst pallet being moved to a side conveyor, illustrating sheets ofmaterial being stacked on the second pallet, and illustrating the palletgrasping assembly en route to obtain a third pallet;

FIG. 37 is a side view of the system of FIG. 1 illustrating the firstpallet on the side conveyor of FIG. 36;

FIG. 38 is a partial detail view of a chain drive system of thedischarge conveyor of FIG. 36;

FIG. 39 is an elevational view of the system of FIG. 1 in accordancewith an alternative embodiment of the present invention illustrating asecond pallet supported by a first pallet and a stack of materials onthe first pallet; and

FIG. 40 is a perspective view of the system of FIG. 1 stacking palletsone another in accordance with the embodiment described in connectionwith FIG. 39.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention, in one form, and suchexemplifications are not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of ordinary skill in the art will understand that thedevices and methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the various embodiments of the present invention is definedsolely by the claims. The features illustrated or described inconnection with one exemplary embodiment may be combined with thefeatures of other embodiments. Such modifications and variations areintended to be included within the scope of the present invention.

In various circumstances, the sheets of material produced by acut-to-length processing line, for example, may be stacked on a pallet,for example, before the sheets of material are transported to adownstream manufacturing process, line, and/or plant. In variouscircumstances, the sheets of material exiting a cut-to-length line canbe fed directly into a sheet stacking system. In other circumstances,the sheets of material may be indirectly fed into a sheet stackingsystem by being held in a staging area and/or be subjected to anintermediate process after exiting the cut-to-length line. In certainembodiments, a sheet stacking system in accordance with variousembodiments of the present invention can include a cut-to-length line,or a portion of a cut-to-length line. In at least some embodiments, thesheet stacking system can include cut-to-width and/or levelerassemblies, for example. In any event, as outlined above and describedin greater detail further below, a sheet stacking and pallet loadingsystem in accordance with various embodiments of the present inventioncan be configured to stack sheets of a material on a first pallet, forexample, while holding a second pallet, for example, in a stagingposition above the first pallet. Such systems can allow the first palletto be quickly replaced with the second pallet after a sufficient, orpredetermined, quantity of sheets have been stacked on the first pallet.In at least one such embodiment, the first pallet can be lowered suchthat it can be unloaded from the sheet stacking system while the secondpallet can be lowered to replace the first pallet with little, or no,interruption to the overall process of stacking sheets of material on apallet. Such a sheet stacking system can facilitate a more efficient andprofitable process, especially when used in conjunction withcontemporaneously operating, and/or integral, cut-to-length, leveling,and/or cut-to-width processing lines. Similar to the above, a thirdpallet can be held in a staging position above the second pallet assheets of material are being stacked on the second pallet, whereby thecycle of replacing full, or at least partially full, pallets with emptypallets can be repeated.

In various embodiments, a sheet stacking and pallet loading system inaccordance with various embodiments of the present invention, such assystem 100 (FIG. 1), for example, can include a pallet loading systemconfigured to obtain one or more pallets from a pallet pick-up area,such as pick-up point 101, for example, and deliver the pallet orpallets to a sheet stacking system. In at least one embodiment, thepallet loading system can include one or more support cantilevers 105for supporting one or more pallets, such as pallets 102, 103, and 104,for example, and a pallet car 106 for transporting the pallets fromsupport cantilevers 105 to a position in which pallet-grasping system120 can remove a pallet from car 106 as described in greater detailbelow. In certain embodiments, car 106 can include a propulsion and/orsteering system which can permit car 106 to move toward cantilevers 105in direction A, for example. As illustrated in FIG. 3, car 106 caninclude wheels 107 which can drive and/or steer car 106. In variousembodiments, car 106 can be configured such that it can be positionedunderneath cantilevers 105 and lift the pallets upwardly off of, or atleast nearly off of, cantilevers 105. In at least one embodiment, car106 can include support surface 108 and, in addition, an elevator 112,such as a hydraulic cylinder and piston assembly and/or a scissorshoist, for example, which can be configured to move support surface 108upwardly into contact with the pallets. In certain embodiments,referring to FIG. 2, support surface 108 can include channels, or slots,110 which can be configured to receive and provide clearance forcantilevers 105, or at least the distal ends of cantilevers 105, whencar 106 is positioned underneath cantilevers 105. In such embodiments,the channels 110 can be sufficiently deep so as to allow support surface108 to be moved upwardly relative to cantilevers 105. Once the palletshave been sufficiently lifted off of cantilevers 105 by support surface108, car 106 can move away from cantilevers 105 in direction B, forexample, and remove the pallets from pallet pickup point 101.

In various embodiments, pallet grasping assembly 120 can be utilized tograsp a pallet on car 106, lift the pallet upwardly, and/or move thepallet to a pallet staging, or delivery, position as described ingreater detail further below. In the exemplary embodiment illustrated inFIGS. 4 and 5, for example, the pallet grasping assembly 120 can beconfigured to grasp one pallet at a time, although alternativeembodiments are envisioned in which a pallet grasping assembly can beconfigured to grasp more than one pallet at a time. In any event,referring to FIGS. 6-11, pallet grasping system 120 can include frame124 and one or more actuator assemblies which can be configured toco-operate with one another to grasp a pallet. In at least oneembodiment, pallet grasping system 120 can include a first actuatorassembly 126, a second actuator assembly 128, and a third actuatorassembly 130 which can each include at least one end-effector forengaging a pallet and at least one actuator for positioning theend-effector. In at least one such embodiment, one or more of theactuator assemblies 126, 128, and 130 can be movably mounted to frame124 such that one or more of the actuator assemblies 126, 128, and 130can be slid toward and/or away from a pallet positioned on car 106, forexample. Referring to FIGS. 6-9, first actuator assembly 126, forexample, can be slidably mounted to frame 124 within first guide 140such that first actuator assembly 126 can be slid along first path 146.In various embodiments, first guide 140 can include sidewalls 141 whichcan define the first path 146 for first actuator assembly 126. In atleast the illustrated embodiment, sidewalls 141 can define substantiallystraight walls and path 146 can be at least partially defined by anaxis. In certain embodiments, referring to FIG. 15, an actuator assemblycan include one or more guide supports 127 which can be configured toslidably support the actuator assembly on one or more guide rails, suchas guide rail 115, for example, which can extend from, and/or be mountedto, frame 124. In at least one embodiment, guide supports 127 and guiderails 115 can include co-operating dovetail features which can permitrelative movement along guide rails 115 but limit transverse movement,or otherwise undesirable movement, therebetween.

In various embodiments, further to the above, first actuator assembly126 can include any suitable means for moving first actuator assembly126 relative to frame 124. In at least one embodiment, first actuatorassembly 126 can include a motor and a drive wheel operably engaged withthe motor. In at least one such embodiment, the drive wheel can be incontact with at least one of sidewalls 141 such that, when the drivewheel is rotated by the motor, the drive wheel can propel first actuatorassembly 126 along first path 146. The direction in which first actuatorassembly 126 is propelled, i.e., toward or away from the pallet, candepend on the direction in which the drive wheel is rotated. Otherembodiments are envisioned in which a rack and pinion arrangement can beutilized to propel first actuator assembly 126. In at least one suchembodiment, referring to FIG. 6, the first actuator assembly 126 caninclude a motor 121, such as a stepper motor, for example, which can beconfigured to rotate a gear 123, such as a pinion gear or spur gear, forexample. Referring primarily to FIG. 8, gear 123 can be meshinglyengaged with a toothed rack 125 mounted adjacent to, and/or mounted on,one or more of sidewalls 141 and/or any other suitable portion of frame124. In use, motor 121 can rotate gear 123 such that, owing to themeshed engagement between the teeth of gear 123 and rack 125, therotation of gear 123 may propel actuator assembly 126 along path 146inwardly and/or outwardly depending on the direction in which gear 123is rotated. Although rack 125 and path 146 are illustrated as having alinear, or at least substantially linear, arrangement, other embodimentsare envisioned in which the rack and/or path include one or more curvedportions and/or one or more linear portions. Furthermore, although notillustrated, other embodiments are envisioned which utilize chain drivesand/or belt drives, for example, for moving one or more of the actuatorassemblies relative to frame 124, for example.

Similar to the above, frame 124 can further include second guide 142 andthird guide 144 which can be configured to guide second actuatorassembly 128 and third actuator assembly 130, respectively, when theyare moved relative to frame 124. In various embodiments, second actuatorassembly 128 can be slidably mounted to frame 124 within second guide142 such that second actuator assembly 128 can be slid along second path148 and, in addition, third actuator assembly 130 can be slidablymounted to frame 124 within third guide 144 such that third actuatorassembly 130 can be slid along third path 150. Also similar to theabove, actuator assemblies 128 and 130 can include any suitable meansfor moving the actuator assemblies 128 and 130 relative to frame 124including means similar to those described in connection with firstactuator assembly 126, for example. In any event, as outlined above, anactuator assembly can be movably or slidably mounted to frame 124, forexample, such that the end-effector of the actuator assembly can bepositioned against a pallet. Referring to FIGS. 6 and 7, first actuatorassembly 126, for example, can include an actuator 132 and, in addition,an end-effector 136 having a pallet-contacting portion 137. Once thepallet-contacting portions 137 are in contact with a pallet, forexample, the actuator assemblies can be configured to apply forces tothe pallet via their respective end-effectors 136. In certainembodiments, such forces can be generated via the drive means, such asmotor 121, gear 123, and rack 125, for example, and transmitted to thepallet through the end-effector 136. Other embodiments are envisioned inwhich the actuator assembly includes an additional system for generatinga force and transmitting the force through the end-effector. In anyevent, the forces applied by the actuator assemblies can be sufficientsuch that the actuator assemblies can hold the pallet therebetween.

In various embodiments, further to the above, the end-effector 136 ofthe first actuator assembly 126 can be moved into engagement with apallet in a first direction, the end-effector 136 of the second actuatorassembly 128 can be moved into engagement with the pallet in a seconddirection, and the end-effector 136 of the third actuator assembly 130can be moved into engagement with the pallet in a third direction. In atleast one such embodiment, the first direction can be defined by firstpath 146, the second direction can be defined by second path 148, andthe third direction can be defined by third path 150. In variousembodiments, as a result of the above, the actuator assemblies of palletgrasping assembly 120 can engage the pallet in three differentdirections. In at least one such embodiment, the actuator assemblies canbe configured to cooperate with one another to hold the pallet in aplane. In some embodiments, the directions in which the end-effectorsengage the pallet can be triangulated, or otherwise arranged, in orderto apply forces to the pallet such that the forces can have differentvector components. In at least one embodiment, referring to FIG. 6,first actuator assembly 126 can be engaged with the pallet in a firstdirection along first path 146 which can be collinear or parallel, or atleast substantially collinear or parallel, to a second direction inwhich second actuator assembly 128 can engage the pallet along secondpath 148. After the end-effectors 136 of actuator assemblies 126 and 128contact the pallet, they can apply forces to the pallet which are inopposite, or at least substantially opposite, directions and thus applyforces in opposite, or at least substantially opposite, directions.Advantageously, further to the above, the pallet grasping assembly 120can be configured to grasp a variety of pallets having different palletwidths, for example. By way of example, the end-effectors 136 may onlyhave to be moved inwardly a short distance when a wide pallet ispositioned therebetween as compared to a longer distance when a narrowerpallet is positioned therebetween.

In various embodiments, further to the above, the end-effector 136 ofthird actuator assembly 130 can be engaged with the pallet in adirection along third path 150 which is perpendicular, or at leastsubstantially perpendicular, to first path 146 and second path 148. Inat least one embodiment, as a result, the actuator assemblies of palletgrasping assembly 120 can be configured to grasp a variety of palletshaving different lengths. More particularly, the third actuator assembly130 may be moved inwardly different distances in order to accommodatepallets having different lengths. By way of example, the end-effectors136 of first and second actuator assemblies 126 and 128 may be movedinwardly to contact a pallet according to its width dimension and thethird actuator assembly 130 may be moved inwardly to contact the palletaccording to its length dimension. In various embodiments, thirdactuator assembly 130 may be brought into contact with the pallet afterthe first and second actuators 126, 128 have already contacted thepallet and are applying forces to the pallet. Thereafter, in at leastone such embodiment, the third actuator assembly 130 can apply a forceto the pallet which is perpendicular, or at least substantiallyperpendicular, to the forces applied by the first and second actuatorassemblies 126 and 128. In various embodiments, although notillustrated, an actuator assembly can include one or more brakes whichcan be configured to engage frame 124, for example, to hold, or at leasttemporarily hold, the actuator assembly in position. In at least oneembodiment, such a brake can be actuated after the actuator assembly hasapplied a force to a pallet such that the actuator assembly can belocked into place to apply a constant force, or at least substantiallyconstant force, to the pallet.

In various alternative embodiments, although not illustrated, the pathsfor moving the actuator assemblies and/or the directions for applyingforces to a pallet may be oriented in skew, transverse, and/or obliquedirections, for example. In at least one alternative embodiment,although not illustrated, a pallet grasping assembly may include one ormore stationary actuator assemblies. More particularly, in at least oneembodiment, a first actuator assembly may be stationary and a secondactuator assembly may be configured to move a pallet against the firstactuator assembly such that the pallet can be held between the first andsecond actuator assemblies. In certain embodiments, although a“stationary” actuator assembly may not be movable relative to itssupporting frame, such as frame 124, for example, an actuator assemblycan be considered to be “stationary” eventhough the actuator assemblycan raise and lower an end-effector as outlined above and described ingreater detail further below. In some embodiments, the pallet mayalready be positioned against the stationary actuator and, in suchcircumstances, the second actuator may abut the pallet to secure itagainst the stationary actuator. Furthermore, although the exemplaryillustrated embodiment includes three actuator assemblies, embodimentsare envisioned having more than or less than three actuator assemblies.

The end-effectors 136 depicted in Figs.12-16, for example, can include aflat, or at least substantially flat, surface which can be configured toabut a pallet as described above. In at least one embodiment, at least aportion of end-effectors 136 can have a rough surface texture,serrations, and/or a raised pattern which can be configured to increasethe coefficient of friction, and/or friction force, between theend-effectors and the pallet. End-effectors 136 are suitable, or evenpreferred in some applications, although other end-effectors inaccordance with various embodiments of the present invention areenvisioned. In certain embodiments, an end-effector can include one ormore projections and/or recesses which can be configured to engage andsupport a pallet. In at least one embodiment, although not illustrated,an end-effector can include a lip extending from a distal portion of theend-effector, for example, wherein the lip can be configured to supporta pallet. In use, in various embodiments, one or more end-effectors canengage or grasp a pallet by being brought into close opposition with thepallet such that a bottom surface of the pallet, for example, issupported by the lips extending from the end-effectors. In suchembodiments, when the end-effectors are raised to lift the pallet, forexample, the end-effectors can apply lifting forces to the pallet viathe lips. In certain embodiments, the end-effectors can also include asurface which can be configured to abut, and/or apply a force to, a sideof the pallet, for example, as described above. In any event, it is tobe understood that the configuration of the end-effectors utilized invarious embodiments may depend on the configuration of pallets to bemoved and, accordingly, the devices and methods described herein can beadapted to grasp or engage such pallets.

Once a pallet grasping assembly has grasped a pallet, the palletgrasping assembly can raise and/or lower the pallet. In variousembodiments, referring again to FIG. 5, pallet grasping assembly 120 canbe configured to lift a pallet off of car 106, for example, once theend-effectors 136 of actuator assemblies 126, 128, and 130 have beenengaged with the pallet. In at least one embodiment, referring to FIGS.12-15, each actuator assembly can include at least one actuator formoving the end-effector. In at least one such embodiment, each actuatorassembly can include an actuator 132 having a piston cylinder 129 and apiston shaft 134 where piston shaft 134 can be hydraulically and/orpneumatically moved relative to piston cylinder 129. As illustrated inFIGS. 12 and 13, an end-effector 136 can be operably connected to pistonshaft 134 such that, when piston shaft 134 is raised or lowered relativeto piston cylinder 129, end-effector 136 can be raised or lowered aswell. Accordingly, when end-effectors 136 are raised, the pallet engagedby the end-effectors 136 can be lifted upwardly and, when end-effectors136 are lowered, the pallet can be lowered downwardly. Althoughembodiments having various couplers, cams, and/or linkages fortransmitting motion and/or forces between piston shaft 134 andend-effector 136 are envisioned, the slider-crank assembly illustratedin FIGS. 12-15 can be utilized. In at least one such embodiment, theslider-crank assembly can include a coupler link 133, a connecting link135, and a frame 138 which can be configured to co-operatively move andguide end-effector 136 as described in greater detail below.

In certain embodiments, piston shaft 134 can include a yoke 131 mountedthereto, or extending therefrom, which can be pinned to coupler link 133such that the extension of piston shaft 134 relative to piston cylinder129 can cause coupler link 133 to rotate about pin 133 a and, inaddition, connecting link 135 to rotate about pin 135 a. Referring toFIGS. 12 and 13, the extension of piston shaft 134 upwardly can causecoupler link 133 to rotate counter-clockwise (as viewed in FIG. 12),wherein the rotation of coupler link 133 can cause connecting link 135to rotate clockwise (again, as viewed in FIG. 12). Coupler link 133 canbe pinned to end-effector 136 via pin 136 a such that the movement ofcoupler link 133 can be transmitted to end-effector 136. For example,when coupler link 133 is rotated counter-clockwise, coupler link 133 canretract, or drive, end-effector 136 upwardly. Correspondingly, whenpiston shaft 134 is moved or pulled downwardly and coupler link 133 isrotated clockwise, coupler link 133 can drive end-effector 136downwardly. In certain embodiments, referring to FIGS. 14 and 15,end-effectors 136 can include one or more rails 139 extending therefromwhich can be received within one or more grooves, or slots, 143 in frame138. When an end-effector 136 is moved by a coupler link 133 asdescribed above, rails 139 and grooves 143 can be sized and configuredto co-operatively define a path for end-effector 136 such thatend-effector 136 slides relative to frame 138 in one of an upward ordownward direction, for example. In various embodiments, rails 139 andgrooves 143 can include co-operating dovetail configurations which can,in at least one embodiment, limit the movement of end-effector 136 alongan axis defined by rails 139. Although not illustrated, otherembodiments are envisioned in which end-effector 136 has one or moregrooves and frame 137 has one or more rails extending therefrom. In anyevent, although end-effectors 136 can be slid in upward and downwarddirections as described above, end-effectors, in accordance withalternative embodiments, can be slid or moved in any suitable direction.

Once a pallet grasping assembly has grasped a pallet, further to theabove, the pallet grasping assembly can translate or move the pallet toa pallet-staging, or delivery, position. In various embodiments,referring primarily to FIGS. 1 and 2, system 100 can further include atrack 160 which can be configured to support and guide pallet graspingsystem 120 as it moves the pallet. In at least one embodiment, track 160can include a first guide beam 162 including a first channel 164, asecond guide beam 166 including a second guide channel 168, and, inaddition, one or more support members for supporting guide beams 162 and166. In at least one embodiment, such support members can include tracksupports or columns 170, floor plates 172 which can be configured tomount columns 170 to the ground and/or otherwise stabilize columns 170,and cross-members 174 which can stiffen track 160 and assist inmaintaining a desirable alignment between first guide channel 164 andsecond guide channel 168.

In various embodiments, pallet grasping system 120 can include anysuitable means for moving the pallet grasping system 120 relative totrack 160. In at least one embodiment, pallet grasping system 120 caninclude one or more motors and one or more drive wheels operably engagedwith the motor(s). In at least one such embodiment, a drive wheel can bein contact with at least one of the sidewalls of guide channel 164and/or guide channel 168 such that, when the drive wheel is rotated by amotor, the drive wheel can propel pallet grasping assembly 120 along apredetermined path. The direction in which assembly 120 is propelled,i.e., toward or away from pick-up point 101, for example, can depend onthe direction in which the drive wheel is rotated. Other embodiments areenvisioned in which a rack and pinion arrangement can be utilized topropel pallet grasping assembly 120. In at least one such embodiment,the assembly 120 can include a motor, such as a stepper motor, forexample, which can be configured to rotate a gear, such as a piniongear, for example, which is meshingly engaged with a toothed rackmounted to and/or otherwise extending from guide beams 162, guide beam166, and/or any other suitable portion of track 160. Other embodimentsare envisioned which utilize chain drives and/or belt drives, forexample, for moving pallet grasping assembly 120. In at least one suchembodiment, referring to FIG. 6, frame 124 of grasping assembly 120 caninclude attachment points 119 which can be used to affix a drive chain,for example, to frame 124 such that the drive chain can impart motion tograsping assembly 120. In certain embodiments, referring to FIG. 11,frame 124 can further include one or more guide supports 117 which canbe operably engaged with one or more guide rails (not illustrated) onguide beam 162, for example, such that guide supports 117 and the guiderails can guide and support pallet grasping assembly 120. Referring toFIGS. 8 and 9, frame 124 can also include guide rollers 115 which can beconfigured to be supported by guide beam 166, for example, andfacilitate relative movement between frame 124 and guide beam 166.

In various embodiments, a pallet grasping assembly can be configured tomove a pallet to a sheet stacking assembly such that sheets of materialcan be stacked on the pallet. In at least one embodiment, referring toFIG. 17, pallet grasping assembly 120 can be configured to move a firstpallet 102 over sheet stacking assembly 200 and lower pallet 102therein. In at least one embodiment, although not illustrated, thepallet grasping assembly 120 can be configured to position pallet 102over elevator 180 and lower the pallet directly onto elevator 180. Inother various embodiments, referring to FIG. 18, the pallet graspingassembly 200 can be configured to lower first pallet 102 onto extendablepallet supports. More particularly, in at least one embodiment, sheetstacking assembly 200 can include one or more extendable pallet supports220 which can be configured to support a pallet beneath first sheetsupport 202, beneath second sheet support 204, and/or above elevator180, which are all described in greater detail below. In variousembodiments, pallet grasping assembly 120 can be configured to center apallet between first sheet support 202 and second sheet support 204, forexample. In at least one such embodiment, the end-effectors 136 ofpallet grasping assembly 120 can be positioned such that, whenend-effectors 136 lower the pallet onto pallet supports 220, forexample, the pallet can be centered, or at least substantially centered,between sheet supports 202 and 204, for example. In various embodiments,track 160 can include a positive stop, or datum, against which palletgrasping assembly 120 can abut in order to repeatably align assembly120, and the pallet held by end-effectors 136, with sheet supports 202and 204. In at least some embodiments, system 100 can further include acomputer which can adjustably position pallet grasping assembly 120,and/or the actuator assemblies movably mounted thereon, relative tosheet stacking system 200 such that a pallet is suitably aligned withsheet supports 202 and 204.

In certain embodiments, referring to FIG. 24, pallet supports 220 caneach include one or more flat, or at least substantially flat, surfaces221 for supporting a pallet. In at least some embodiments, although notillustrated, at least a portion of pallet supports 220, for example, caninclude projections, recesses, and/or any other suitable configurationwhich can be configured to retain a pallet thereon. Referring primarilyto FIG. 21, first frame rail 212 can include one or more guide apertures213 which can be configured to slidably support and guide one or morerod assemblies 215 which can be attached to, or otherwise operablycoupled with, one or more extendable pallet supports 220.

Referring to FIGS. 21 and 24, supports 220 can be extended from and/orretracted relative to first frame rail 212 and/or second frame rail 214by one or more actuators (not illustrated in this embodiment), such ashydraulic and/or pneumatic cylinder assemblies, for example, which canbe operably coupled to pallet supports 220 and/or rod assemblies 215.Referring to the embodiment illustrated in FIGS. 28-33, a sheet stackingassembly can include one or more extendable pallet supports 320 whichcan be extended relative to frame rail 312 by actuators 317. In at leastone such embodiment, an actuator 317 can include a cylinder 319 mountedto, or at least relative to, frame rail 312 and, in addition, a pistonrod 315 which can be extended and/or retracted relative to cylinder 319.In various embodiments, a pallet support 320 can be moved between afirst, or extended, position illustrated in FIG. 28 and a second, orretracted, position illustrated in FIG. 32. In at least one embodiment,referring again to FIG. 28, frame rail 312 can further include one ormore bearings 325 which can be configured to slidably support one ormore pallet supports 320. In certain embodiments, referring now to FIG.33, a pallet support 320 can include one or more cylindrical, or atleast substantially cylindrical, members 323 which can be slidablyreceived within bearings 325. Similar to the above, in at least oneembodiment, cylindrical members 323 can include flat surfaces 321 whichcan be configured to support a pallet as outlined above.

As discussed above, referring again to FIG. 18, pallet grasping assembly120, for example, can be configured to position first pallet 102, forexample, on extendable pallet supports 220. In various embodiments,first rail 212 and/or second rail 214 may be moved away from each otherto allow the pallet grasping assembly 120 and the pallet 102, forexample, to pass by first and second sheet supports 202, 204, forexample, as pallet 102 is placed on pallet supports 220. Stated anotherway, owing to certain configurations of sheet supports 202 and 204, forexample, rail 212 and/or rail 214 may have to be slid outwardly suchthat the end-effectors 136 of pallet grasping assembly 120 do notcollide with, or are unsuitably impeded by, rails 212 and 214. Incertain embodiments, referring to FIG. 19, rail 312, for example, can beslidably supported by frame 161 such that rail 312 can be slid between afirst, or inward, position (shown in solid lines in FIG. 19) and asecond, or outward, position (shown in phantom lines in FIG. 19). Inorder to move rail 312, sheet stacking system 200 can further includeone or more actuator assemblies 260. In at least one embodiment, anactuator assembly 260 can include a jack screw, or lead screw,arrangement which can be configured to adjustably position rail 312. Invarious embodiments, referring to FIG. 19, each actuator assembly 260can include one or more threaded shafts 262, one or more motors 264 fordriving shafts 262, and, in addition, one or more distal end-effectors266 operably connected to rail 312. In at least one embodiment, a motor264 can include a rotatable member, or shaft, operably engaged with athreaded shaft 262 such that, when the motor shaft is rotated, thethreaded shaft 262 can be displaced along axis 265. Depending on thedirection in which the motor shaft is rotated, the motor 264 can drivethe threaded shaft 262 in one of an inward or an outward direction. Invarious embodiments, referring again to FIG. 19, rail 312 can furtherinclude one or more guide supports 313 which can be configured toco-operate with one or more guides 311 to define a path for rail 312. Inat least one embodiment, guide 311 can be mounted to or extend fromframe 161, for example. In various embodiments, such a path can belinear, or at least substantially linear, although, in at least someembodiments, the path can include one or more curved portions and/or oneor more linear portions. In any event, after the first pallet 102 hasbeen placed onto the pallet supports, the frame rails can be movedinwardly once again.

Once first pallet 102 is supported, sheet stacking assembly 200 can beconfigured to stack sheets of material, such as one or more sheets ofmaterial 190 (FIG. 20), for example, onto pallet 102. In variousembodiments, the sheets of material can be comprised of sheet steel,cold-rolled steel, hot-rolled steel, stainless steel, steel alloys,copper, copper alloys, brass alloys, aluminum, aluminum alloys, and/orany other suitable metal and/or non-metal, for example. As outlinedabove, referring to FIG. 20, sheet stacking assembly 200 can include oneor more sheet supports, such as first sheet support 202 and second sheetsupport 204, for example, which can be configured to receive and supportone or more sheets of material. In at least one embodiment, referring toFIG. 21, one or more of the sheet supports can include rollers 206 whichcan facilitate relative sliding movement, and/or other suitable relativemovement, between the sheet of material and sheet supports 202 and 204,for example. In certain embodiments, referring to FIG. 22, sheet ofmaterial 190 can include a first edge portion 194 which can be supportedby the first sheet support 202 and, in addition, a second edge portion196, which can be supported by the second sheet support 204. In certainembodiments, a sheet stacking assembly can include end stops, such asbackstop 208 (FIG. 20), for example, which can be configured to controlthe position, and/or limit the movement, of sheet 190 on sheet supports202 and 204. In at least one such embodiment, referring again to FIG.22, the sheet of material 190 can be slid onto sheets supports 202 and204 until back edge 192 of sheet 190, for example, contacts backstop208. Furthermore, although not illustrated, sheet stacking assembly 200can further include one or more front stops for controlling, or limitingthe movement of, the front edges of sheets 190, for example. Althoughthe sheets of material in the illustrated embodiments are rectangular,or at least substantially rectangular, and have readily definable edges,other embodiments are envisioned in which the sheets of material canhave any suitable shape or shapes.

Once a sheet, or sheets, of material have been positioned on the sheetsupports, such as sheet supports 202 and 204, for example, the sheet(s)of material may be stacked on a pallet. In various embodiments,referring to FIG. 23, sheet supports 202 and 204 can be configured tolower, or drop, sheet 190 onto pallet 102. In at least one suchembodiment, first sheet support 202 can be rotatably supported by firstframe rail 212 and, similarly, second sheet support 204 can be rotatablysupported by second frame rail 214 such that, referring to FIG. 24, thesheet supports 202 and 204 can be configured to rotate, or pivot,downwardly with respect to frame rails 212 and 214 about pivots 210.Thereafter, sheet supports 202 and 204 can be rotated upwardly such thatthey can receive and support another sheet of material. In variousembodiments, sheet supports 202 and 204 can be raised and lowered byhydraulic and/or pneumatic actuators, for example. In at least one suchembodiment, referring to FIGS. 28 and 29, an actuator 280 can beoperably connected to sheet support 202 and frame rail 212, for example,and can be configured to rotate sheet support 202 between a down, orsheet-dropping, position illustrated in FIG. 28 and an up, orsheet-supporting, position illustrated in FIG. 29. In at least oneembodiment, actuator 280 can include a piston cylinder 282 mounted toframe rail 312, for example, and, in addition, a piston rod 284 whichcan be moved relative to piston cylinder 282 between a retractedposition (FIG. 28) and an extended position (FIG. 29). Although notillustrated, other embodiments are envisioned in which a motor, forexample, can be used to rotate sheet support 202 relative to frame rail212, for example.

In embodiments where first pallet 102 is not initially placed onelevator 180, the elevator 180 can be raised upwardly to support pallet102 positioned on the extendable pallet supports. In variousembodiments, referring to FIG. 25, elevator 180 can be raised upwardlysuch that pallet support surface 182 is positioned beneath pallet 102.In at least one such embodiment, elevator 180 can include one or morehydraulic and/or pneumatic lifts, such as lifts 181, for example, whichcan be configured to raise and lower pallet support surface 182. In anyevent, referring to FIG. 31, pallet support surface 182 can, in variousembodiments, be positioned against at least a portion of pallet 102, forexample, in order to at least partially support and/or raise pallet 102off of the pallet supports. In at least one such embodiment, referringto FIG. 40, pallet support surface 182 can include one or more recesses183 therein which can be configured to receive and accommodate palletsupports 220, for example, when they are in their extended position. Inany event, once pallet 102 is at least partially supported by elevator180, referring to FIG. 32, the extendable pallet supports can then beretracted such that pallet 102 is supported only by elevator 180. Oncepallet 102 is supported by elevator 180, referring to FIGS. 26 and 27,elevator 180 can be indexed downwardly in order to control the distancein which the sheets of material 190 fall onto pallet 102, for example.

As outlined above, another pallet can be moved into a staging positionabove the first pallet as the sheets of material are being stacked onthe first pallet. In various embodiments, referring to FIGS. 25-27,pallet grasping system 120 can be configured to grasp a second pallet,such as pallet 103, for example, and position pallet 103 above firstpallet 102 as sheets of material are being stacked onto first pallet102. In such embodiments, as described in greater detail further below,the first pallet 102 can be quickly replaced with the second pallet 103with little, or no, interruption, to the material stacking process. Asoutlined above, the process of stacking or dropping sheets of materialonto the first pallet can be repeated until a sufficient, orpredetermined, quantity of sheets has been stacked on the first pallet.In various circumstances, a sufficient quantity of sheets can include astack of sheets which is at or near the capacity that the pallet cansupport or, alternatively, a sufficient quantity of sheets can include astack of sheets which is less than such capacity. In any event, once asufficient, or predetermined, quantity of sheets has been placed ontofirst pallet 102, referring to FIG. 34, the elevator 180 can lowerpallet 102 downwardly. In various embodiments, elevator 180 can lowerpallet 102 such that pallet 102 and the sheets of material stackedthereon are positioned beneath sheet supports 202 and 204, for example.While the first pallet 102 is being lowered away from sheet supports 202and 204, pallet grasping assembly 120 can lower second pallet 103 towardsheet supports 202 and 204. In various embodiments, extendable supports220, for example, can be configured to support second pallet 103 whilefirst pallet 102 is unloaded from elevator 180 and, simultaneously,while sheets of material are stacked on second pallet 103. Such a systemcan provide a significant advantage over other sheet stacking systemsthat must wait for a first, or full, pallet to be unloaded from thesheet stacking system before a second pallet can be positioned withinthe sheet stacking system to receive sheets of material thereon. Furtherto the above, various embodiments are envisioned in which the secondpallet 103 can be lowered toward the first pallet 102 before the firstpallet 102 is lowered by the elevator 180 such that the first pallet 102can be immediately replaced by the second pallet 103 once the firstpallet 102 is lowered.

After the first pallet 102 has been lowered by the elevator 180 asdescribed above, the first pallet 102 can be unloaded from the elevator180 onto a conveyor. More particularly, referring to FIGS. 35-38, sheetstacking assembly 200 can further include discharge conveyor 230 whichcan be configured to move first pallet 102 off of elevator 180 afterpallet support surface 182 of elevator 180 has been sufficiently loweredbelow the top surfaces of support beams 236. Stated another way, oncepallet support surface 182 is moved below the top surfaces of supportbeams 236, the pallet 102 can be entirely supported on beams 236 and canbe moved along beams 236 by one or more drive systems. In variousembodiments, one or more of the beams 236 can include a drive systemwhich can be configured to move pallet 102 along discharge conveyor 230as illustrated in FIG. 36. Among other things, a drive system caninclude one or more drive belts, chains, and/or bands, for example,which can be configured to engage pallet 102 and slide it toward centralconveyor 240. In certain embodiments, referring to FIG. 38, a beam 236can include a chain drive mounted thereto comprising a drive chain 232,for example, which can be configured to pull pallet 102 off of elevator180. In at least one such embodiment, one or more beams 236 can includeone or more sprockets 234, for example, rotatably mounted to beams 236which can define a path for drive chains 232. Support beams 236 canfurther include one or more motors (not illustrated) operably engagedwith one or more of the sprockets 234 such that drive chains 232 can bedriven around support beams 236. In at least one such embodiment, drivechains 232 can be pulled in a direction indicated by arrow C, forexample. More particularly, when a pallet is positioned on beams 236 asoutlined above, drive chains 232 can be positioned intermediate thepallet and beams 236 such that the drive chains 232 can move the pallettoward central conveyor 240. In various embodiments, referring to FIG.38, the ends of beams 236, for example, can include inset portions 238within which sprockets 234, for example, can be rotatably mounted tobeams 236 such that sprockets 234 and/or chains 232 can be aligned, orat least substantially aligned, with the longitudinal axes of beams 236.

All the while the first pallet is unloaded from the sheet stackingassembly, further to the above, sheets of material can be stacked ontosecond pallet 103 as outlined above. Furthermore, sheets of material cancontinue to be stacked on second pallet 103 while the elevator 180 ispositioned underneath second pallet 103 and, furthermore, when theextendable pallet supports 220 are retracted and the second pallet 103is supported by elevator 180. Similar to the above, a third pallet 104can be obtained by pallet grasping system 120, referring generally toFIG. 36, and positioned over the second pallet 103 in a staging positionwhile the sheets of material are stacked onto the second pallet 103.Also similar to the above, once a sufficient, or predetermined, quantityof sheets have been stacked on the second pallet 103, the second pallet103 can be lowered by elevator 180 and the third pallet 104 can belowered to allow sheets of material to be stacked thereon. As before,such a system allows for a quick and efficient exchange of palletswherein such a pallet exchange process can be repeated as many times asdesired and/or possible.

In various embodiments, as described above, pallet grasping system 120can be configured to move back and forth in order to obtain and deliverone pallet at a time. Although not illustrated, other alternativeembodiments are envisioned in which a pallet grasping system can obtainmore than one pallet at a time, hold the additional pallets above thesheet stacking assembly, and deliver them to the sheet stacking devicewhen needed. In the various embodiments described herein, the palletgrasping system 120 is often described as holding one or more pallets‘above’ the sheet stacking assembly and/or the sheet supports of thesheet stacking assembly, for example. While, in some embodiments, theterm ‘above’ may describe a vertical position which is directly over thesheet stacking device and/or sheet supports, the term ‘above’ is alsomeant to include any suitable location in which and/or from which apallet can be delivered downwardly to the sheet stacking device, forexample. Furthermore, as outlined above, the devices and systemsdescribed herein can be utilized to stack sheets of material on“pallets; however any suitable platform, container, and/or any othersuitable device for stacking material thereon are all considered to beencompassed by the term “pallet”.

In order to facilitate the unloading of stacked pallets from sheetstacking assembly 200, referring to FIG. 37, system 100 can furtherinclude one or more additional roller conveyors for storing, or at leasttemporarily supporting, one or more pallets before they are removed fromsystem 100. In various embodiments, system 100 can further include aleft roller conveyor 248 and a right roller conveyor 250 where palletspositioned on central conveyor 240 can be moved onto conveyors 248 and250. In at least one embodiment, central conveyor 240 can include afirst end 244, a second end 246, and one or more lifts, hoists, and/orany other suitable lifting devices (not illustrated) which can raiseand/or lower ends 244 and 246. In at least one such embodiment, firstend 244 can be raised above second end 246 such that a pallet on centralconveyor 240 can slide toward and onto right roller conveyor 250. Incertain embodiments, central conveyor 240 can include one or more rollersupports 242 which can be configured to facilitate relative slidingmovement between the pallet and central conveyor 240. In at least oneembodiment, similar to the above, second end 246 can be raised abovefirst end 244 such that a pallet on central conveyor 240 can slidetoward and onto left roller conveyor 248. In various embodiments, bothends 244 and 246 can be raised, although one more than the other, inorder to tilt central conveyor 240. In certain embodiments, one of ends244 and 246 can be raised and the other of ends 244 and 246 can belowered in order to tilt central conveyor 240. In at least oneembodiment, both ends 244 and 246 can be lowered, although one more thanthe other. In any event, both conveyors 248 and 250 can include rollersupports 242 which can facilitate the movement of a pallet from centralconveyor 240 thereon.

In various embodiments, as described above, a pallet having asufficient, or predetermined, quantity of sheets thereon can be loweredby elevator 180, for example, and unloaded therefrom. In certainembodiments, however, a pallet, such as first pallet 102, for example,may be lowered by elevator 180 but may remain on elevator 180. In atleast one embodiment, referring to FIG. 39, system 100 can be configuredto position a second pallet, such as second pallet 103, for example, ontop of first pallet 102. In at least one such embodiment, second pallet103 may be positioned on top of the sheet stack supported by firstpallet 102. In alternative embodiments, although not illustrated, thefirst and second pallets can be configured such that the second palletis directly supported by the first pallet. Such embodiments can allowthe pallets to be stacked on one another without contacting ordisrupting the stack of materials. In any event, in at least oneembodiment, one or more additional pallets may be stacked on the secondpallet. In various embodiments, once a sufficient, or predetermined,quantity of sheets have been stacked on the pallets, and a sufficient,or predetermined, quantity of pallets has been stacked on one another,the elevator 180 can be unloaded. In at least one embodiment, referringto FIG. 40, for example, the stack of pallets can be unloaded fromelevator 180 by discharge conveyor 230 in a suitable manner, includingthose described above, for example.

While several embodiments of the invention have been described, itshould be apparent, however, that various modifications, alterations andadaptations to those embodiments may occur to persons skilled in the artwith the attainment of some or all of the advantages of the presentinvention. It is therefore intended to cover all such modifications,alterations and adaptations without departing from the scope and spiritof the present invention as defined by the appended claims.

1. A pallet loading system, comprising: a track defining a path; a framemovable along the path between a pallet-obtaining position and apallet-delivering position; a first pallet-engaging assembly comprising:a first actuator movably mounted to said frame; and a first end-effectoroperably coupled with said first actuator, wherein said first actuatoris configured to move said first end-effector into engagement with thepallet in a first direction; a second pallet-engaging assemblycomprising: a second actuator movably mounted to said frame; and asecond end-effector operably coupled with said second actuator, whereinsaid second actuator is configured to move said second end-effector intoengagement with the pallet in a second direction; and a thirdpallet-engaging assembly comprising: a third actuator movably mounted tosaid frame; and a third end-effector operably coupled with said thirdactuator, wherein said third actuator is configured to move said thirdend-effector into engagement with the pallet in a third direction,wherein said first direction, said second direction, and said thirddirection are different.
 2. The pallet loading system of claim 1,wherein said frame further comprises a first actuator guide, a secondactuator guide, and a third actuator guide, wherein said first actuatoris movable relative to said frame along said first actuator guide,wherein said second actuator is movable relative to said frame alongsaid second actuator guide, and wherein said third actuator is movablerelative to said frame along said third actuator guide.
 3. The palletloading system of claim 2, wherein said first direction is substantiallyparallel to said second direction, and wherein said third direction issubstantially perpendicular to said first direction and said seconddirection.
 4. The pallet loading system of claim 2, wherein said thirddirection is transverse to at least one of said first direction and saidsecond direction.
 5. The pallet loading system of claim 1, wherein saidfirst actuator is further configured to extend said first end-effectoraway from said frame in a direction transverse to said first direction,wherein said second actuator is further configured to extend said secondend-effector away from said frame in a direction which is transverse tosaid second direction, and wherein said third actuator is furtherconfigured to extend said third end-effector away from said frame in adirection which is transverse to said third direction.
 6. The palletloading system of claim 1, wherein said first actuator is configured toextend and retract said first end-effector in a substantially verticaldirection, wherein said second actuator is configured to extend andretract said second end-effector in a substantially vertical direction,and wherein said third actuator is configured to extend and retract saidthird end-effector in a substantially vertical direction.
 7. The palletloading system of claim 1, wherein said first direction is substantiallyparallel to said second direction, and wherein said third direction issubstantially perpendicular to said first direction and said seconddirection.
 8. A sheet stacking system, comprising: a frame; an elevatorhaving at least one pallet support surface configured to support a firstpallet in an elevated position; a first sheet support configured toreceive and support a first sheet of material, wherein said first sheetsupport is rotatably mounted relative to said frame, and wherein saidfirst sheet support is rotatable between a sheet-receiving position anda sheet-dropping position; a second sheet support configured to receiveand support the first sheet of material, wherein said second sheetsupport is rotatably mounted relative to said frame, wherein said secondsheet support is rotatable between a sheet-receiving position and asheet-dropping position, wherein said first and second sheet supportsare configured to drop the first sheet of material onto the first palletwhen said first and second sheet supports are rotated into theirsheet-dropping positions, wherein said first and second sheet supportsare configured to receive a second sheet of material when said first andsecond sheet supports are rotated back into their sheet-receivingpositions, and wherein said first and second supports are configured tostack the second sheet of material onto the first sheet of material whensaid first and second sheet supports are rotated into theirsheet-dropping positions once again; a pallet loading system configuredto hold a second pallet above the first pallet, wherein said elevator isconfigured to move the first pallet between the elevated position and alower position after a sufficient quantity of sheets of material havebeen stacked on the first pallet; at least one first extendable palletsupport; and at least one second extendable pallet support, wherein saidfirst and second extendable pallet supports are configured to supportthe second pallet after they have been extended.
 9. The sheet stackingsystem of claim 8, wherein said first and second extendable palletsupports are retractable, and wherein said elevator is configured toreposition said at least one pallet support surface beneath the secondpallet in order to support the second pallet after said first and secondextendable pallet supports have been retracted.
 10. The sheet stackingsystem of claim 8, wherein said first and second extendable palletsupports are slidably mounted relative to said frame.
 11. The sheetstacking system of claim 8, wherein said first and second extendablepallet supports are configured to be extended as said elevator islowered from said elevated position.
 12. The sheet stacking system ofclaim 8, wherein said first and second sheet supports are slidablymounted relative to said frame.
 13. A method of stacking sheets ofmaterial, comprising: positioning a first pallet on an elevator;stacking sheets of material on the first pallet; positioning a secondpallet above the first pallet; lowering the first pallet after apredetermined quantity of sheets have been stacked on the first pallet;extending pallet supports for supporting the second pallet; and loweringthe second pallet onto the pallet supports.
 14. The method of claim 13,further comprising the steps of: removing the first pallet from theelevator; positioning the elevator beneath the second pallet; andretracting the pallet supports such that the second pallet can besupported by the elevator.
 15. The method of claim 14, furthercomprising the steps of: stacking sheets of material on the secondpallet; positioning a third pallet above the second pallet; lowering thesecond pallet after a predetermined quantity of sheets have been stackedon the second pallet; extending the pallet supports for supporting thethird pallet; and lowering the third pallet onto the pallet supports.16. The method of claim 14, wherein said second pallet is positionedabove the first pallet as sheets of material are stacked onto to thefirst pallet.
 17. The method of claim 14, further comprising the stepsof: positioning the elevator and the first pallet beneath the secondpallet; and retracting the pallet supports such that the second palletcan be supported by at least one of the first pallet and the sheets ofmaterial stacked on the first pallet.
 18. A pallet loading system,comprising: a track defining a path; a frame movable along the pathbetween a pallet-obtaining position and a pallet-delivering position; afirst pallet-engaging assembly comprising: a first actuator movablymounted to said frame; and a first end-effector operably coupled withsaid first actuator, wherein said first actuator is configured to movesaid first end-effector into engagement with the pallet in a firstdirection; a second pallet-engaging assembly comprising: a secondactuator movably mounted to said frame; and a second end-effectoroperably coupled with said second actuator, wherein said second actuatoris configured to move said second end-effector into engagement with thepallet in a second direction, and wherein said first direction and saidsecond direction are different; and a stationary third pallet-engagingassembly, wherein said third pallet-engaging assembly comprises a thirdend-effector which is extendable relative to said frame.